package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;
import com.lagou.utils.TokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * @author HuanyuZhou
 * @date 2020/4/23 14:53
 */
public class SimpleExecutor implements  Executor{

    private final String WrapperClass[] ={"java.lang.Integer","java.lang.String","java.lang.double",
                                            "java.lang.Byte","java.lang.Short","java.lang.Integer",
                                                "java.lang.Float","java.lang.Boolean","java.lang.Character"};


    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        //2.获取sql语句 select * from user where id =#{id} and username = #{username}
        //转换sql语句  select * from user where id = ? and username = ?,转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
            //获取到了参数的全路径
        String parameterType = mappedStatement.getParameterType();
        //反射获取参数类型
        Class<?> parameterClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射 通过属性名字获取参数类的属性
            Field declaredField = parameterClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            //获取参数中该属性的值
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1,o);

        }
        //5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //6.封装返回结果集

        while(resultSet.next()){
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或则内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);

            }
            objects.add(o);
        }

        return(List<E>) objects;
    }

    @Override
    public Integer update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        Connection connection = configuration.getDataSource().getConnection();
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        String parameterType = mappedStatement.getParameterType();
        if(Arrays.asList(WrapperClass).contains(parameterType)){
            preparedStatement.setObject(1,params[0]);
        }else {
            //反射获取参数类型
            Class<?> parameterClass = getClassType(parameterType);
            List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
            for (int i = 0; i < parameterMappingList.size(); i++) {
                ParameterMapping parameterMapping = parameterMappingList.get(i);
                String content = parameterMapping.getContent();
                //反射 通过属性名字获取参数类的属性
                Field declaredField = parameterClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                //获取参数中该属性的值
                Object o = declaredField.get(params[0]);

                preparedStatement.setObject(i + 1, o);

            }
        }
        //5.执行sql
        Integer result = preparedStatement.executeUpdate();

        return result;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {

        if(parameterType != null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作.1.将#{}使用？进行代替。2。解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配合标记解析器完成对位占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来额参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;




    }
}
